James Maddison must be focused to cement an England spot, manager Gareth Southgate said.
England manager Gareth Southgate urged James Maddison to become a "high-performance, low-maintenance" player.
The uncapped Leicester City star, 22, was named in England's squad for this month's Euro 2020 qualifiers against Montenegro and Kosovo.
Maddison, who has three goals and two assists in the Premier League this season, was pictured in a casino after pulling out of the last squad due to illness.
Southgate said the attacker needed to remain focused as he tries to cement a spot in the England setup.
"It's not a good situation for a player when we're talking about him in Sofia, and talking about him here and he's yet to get on the pitch for us," he told UK newspapers.
"So, that's the challenge. You want to be high-performance, low-maintenance. I am prepared to work with players who are more difficult but you're more likely to back those players if they've scored a winner for you and sweated blood for you, and that's the bond you build with those players over a longer period of time."
England are top of Group A in Euro 2020 qualifying, sitting three points clear of the second-placed Czech Republic.
Maddison could make his England debut this month, but Southgate revealed he felt no need to call the midfielder before his latest call-up.
"I didn't feel the need to make a special case to call him. I wanted to see whether we would be selecting on form," he said.
"I think it would be dangerous territory for me to go on a moral crusade over something that I don't think was a good decision but was in his own time and we had released him from the squad."
England host Montenegro at Wembley on Thursday before facing Kosovo in Pristina three days later.